Characterization of a novel rolling-sliding hybrid bearing for main shafts of high-power wind turbines

Traditional main shaft rolling bearings often experience localized stress concentration, transient overheating, and fatigue spalling under low-speed, heavy-load, and variable-speed operating conditions, making it difficult to meet long-life service requirements. To address this issue, this paper proposes a novel hybrid rolling-sliding bearing structure with a parallel design of rolling and sliding bearings, and investigates its operational performance through simulation. Via parameter optimization, the length-to-diameter ratio of the sliding bearing is determined as 1.4, and the initial radial clearance as 400 μm. The results show that under two typical operating conditions of 8 rpm and 10 rpm, the sliding bearing system can achieve a static equilibrium state. Based on the Reynolds equation and its static equilibrium conditions, the eccentricity ratio and attitude angle of the sliding bearing at the static equilibrium position are determined. These parameters are then applied as the eccentric parameters of the bearing bush in the design of the hybrid bearing structure. Consequently, once the hybrid bearing transitions from the start-stop phase to stable operation, the sliding bearing can generate hydrodynamic effects and effectively share the radial load, thereby significantly reducing the radial load borne by the rolling bearing. By adopting a parallel load-carrying structure of rolling and sliding bearings, the modified rating life of the rolling elements within the hybrid bearing under load-sharing conditions reaches approximately 43.52 years at 8 rpm and 35.43 years at 10 rpm, corresponding to improvement factors of 4.9 and 5.0, respectively, compared to the pure rolling bearing, which exhibits 8.89 years at 8 rpm and 7.11 years at 10 rpm. Furthermore, over the operating speed range of 3 to 16 rpm, the average Modified rating life of the rolling elements within the hybrid bearing under load-sharing conditions is approximately 23.58 years for the design based on 8 rpm eccentricity parameters and approximately 23.79 years for the design based on 10 rpm eccentricity parameters, compared to 9.55 years for the pure rolling bearing. The service life of the system is markedly improved, meeting the long-life operation requirements of wind turbines.